Buggy code:
public class Check < T > extends WebMarkupContainer < T > { private static final long serialVersionUID = 1L ; private static final String ATTR_DISABLED = "disabled" ; public Check ( MarkupContainer parent , String id ) { } public Check ( MarkupContainer parent , String id , IModel < T > model ) { } @ Override protected void onComponentTag ( final ComponentTag tag ) { super . onComponentTag ( tag ) ; checkComponentTag ( tag , "input" ) ; checkComponentTagAttribute ( tag , "type" , "checkbox" ) ; CheckGroup < ? > group = Check . findParent ( CheckGroup . class ) ; String path = Check . getPath ( ) ; if ( group == null ) { throw new WicketRuntimeException ( ( ( "Check<seq2seq4repair_space>component<seq2seq4repair_space>[" + path ) + "]<seq2seq4repair_space>cannot<seq2seq4repair_space>find<seq2seq4repair_space>its<seq2seq4repair_space>parent<seq2seq4repair_space>CheckGroup.<seq2seq4repair_space>All<seq2seq4repair_space>Check<seq2seq4repair_space>components<seq2seq4repair_space>must<seq2seq4repair_space>be<seq2seq4repair_space>a<seq2seq4repair_space>child<seq2seq4repair_space>of<seq2seq4repair_space>or<seq2seq4repair_space>below<seq2seq4repair_space>in<seq2seq4repair_space>the<seq2seq4repair_space>hierarchy<seq2seq4repair_space>of<seq2seq4repair_space>a<seq2seq4repair_space>CheckGroup<seq2seq4repair_space>component." ) ) ; } String relativePath = path . substring ( ( ( group . getPath ( ) . length ( ) ) + 1 ) ) ; tag . put ( "name" , group . getInputName ( ) ) ; tag . put ( "value" , relativePath ) ; Collection collection = ( ( Collection ) ( group . getModelObject ( ) ) ) ; if ( collection == null ) { throw new WicketRuntimeException ( ( ( "CheckGroup<seq2seq4repair_space>[" + ( group . getPath ( ) ) ) + "]<seq2seq4repair_space>contains<seq2seq4repair_space>a<seq2seq4repair_space>null<seq2seq4repair_space>model<seq2seq4repair_space>object,<seq2seq4repair_space>must<seq2seq4repair_space>be<seq2seq4repair_space>an<seq2seq4repair_space>object<seq2seq4repair_space>of<seq2seq4repair_space>type<seq2seq4repair_space>java.util.Collection" ) ) ; } if ( group . hasRawInput ( ) ) { String rawInput = group . getRawInput ( ) ; if ( ( rawInput != null ) && ( ( rawInput . indexOf ( relativePath ) ) != ( - 1 ) ) ) { tag . put ( "checked" , "checked" ) ; } } else if ( collection . contains ( Check . getModelObject ( ) ) ) { tag . put ( "checked" , "checked" ) ; } if ( group . wantOnSelectionChangedNotifications ( ) ) { final CharSequence url = group . urlFor ( INTERFACE ) ; Form form = ( ( Form ) ( group . findParent ( Form . class ) ) ) ; if ( form != null ) { tag . put ( "onclick" , form . getJsForInterfaceUrl ( url ) ) ; } else { <START_BUG> tag . put ( "onclick" , ( ( ( ( "location.href='" + url ) + "&" ) + ( group . getInputName ( ) ) ) + "='<seq2seq4repair_space>+<seq2seq4repair_space>this.value;" ) ) ; <END_BUG> } } if ( ( ( ! ( isActionAuthorized ( ENABLE ) ) ) || ( ! ( Check . isEnabled ( ) ) ) ) || ( ! ( group . isEnabled ( ) ) ) ) { tag . put ( Check . ATTR_DISABLED , Check . ATTR_DISABLED ) ; } } }

Fix:
tag . put ( "onclick" , ( ( ( ( "window.location.href='" + url ) + "&" ) + ( group . getInputName ( ) ) ) + "='<seq2seq4repair_space>+<seq2seq4repair_space>this.value;" ) ) ;